Child protected by glowing bubbles, symbolizing varicella immunity

Varicella Vaccine Immunity: Are We Measuring It Right?

Lena Voss in Health & Wellness December 2025 • 5 min read.

"A closer look at the accuracy of current testing methods for varicella immunity and why re-evaluation may be needed for better protection."

For decades, the varicella vaccine has been a cornerstone of pediatric healthcare, significantly reducing the prevalence of chickenpox. The introduction of widespread vaccination programs has dramatically changed the landscape of this once common childhood ailment. With the success of these programs, there's an increasing need to accurately assess vaccine-induced immunity to ensure ongoing protection, especially as breakthrough infections still occur. This need has driven the development and use of various serological assays, each with its own strengths and limitations.

Among the array of available tests, the glycoprotein enzyme-linked immunosorbent assay (gpEIA) holds promise for its ability to detect and quantify antibodies against VZV. The VaccZyme™ VZV gpEIA kit, a commercially available assay, aims to standardize immunity measurements by using the WHO international standard as a calibrator. This article explores the effectiveness and reliability of the VaccZyme™ VZV gpEIA kit, comparing its results to the established fluorescent antibody to membrane antigen (FAMA) test, often considered the 'gold standard.'

We delve into a study conducted to evaluate the accuracy and reproducibility of the VaccZyme™ VZV gpEIA kit. This analysis seeks to determine whether current cutoff values—the thresholds used to define immunity—are appropriate for assessing protection in vaccinated children. The goal is to fine-tune our understanding of varicella immunity, potentially improving the effectiveness of vaccination strategies and reducing the incidence of breakthrough infections.

Decoding Varicella Immunity: Why Accuracy Matters

Child protected by glowing bubbles, symbolizing varicella immunity

The varicella vaccine has been used in Korea since 1988 and has been included in a routine vaccination program for children (with a single dose schedule) since 2005. Evaluating the effectiveness of varicella vaccines isn't as straightforward as it seems. The challenge lies in accurately measuring the body's immune response, particularly in vaccinated individuals, where the response may be lower compared to natural infection. Numerous methods exist to detect antibodies against VZV, but each has its own set of limitations regarding objectivity, sensitivity, and ease of use. Because of the need to continue to evaluate the vaccines.

The fluorescent antibody to membrane antigen (FAMA) test is often regarded as the gold standard for detecting varicella antibodies. However, it’s labor-intensive and not easily automated, making it impractical for routine, high-throughput testing. This is where the VaccZyme™ VZV gpEIA kit comes in, offering a potentially more convenient and standardized method for assessing varicella immunity. The kit measures IgG antibodies specific to VZV glycoproteins, using the WHO international standard as a calibrator.

FAMA Test: Considered the gold standard but is labor-intensive and difficult to automate.
gpEIA Test: Aims to offer a more convenient, standardized method using the WHO international standard for calibration.
Objective: To evaluate the accuracy and reliability of the VaccZyme™ VZV gpEIA kit and compare it to the FAMA test.

To evaluate the commercial VZV gpEIA kit, a total 349 sera were included, the study compared the VaccZyme™ VZV gpEIA kit to the FAMA test using sera from 349 children aged 1 to 6 years. The researchers assessed the kit's accuracy, reproducibility, sensitivity, and specificity. The results showed that the VaccZyme™ VZV gpEIA kit provided precise and reproducible results, with a strong linear correlation to FAMA titers. However, when using the kit's recommended cutoff values, the sensitivity was relatively low, indicating that the standard guidelines might not be optimal for vaccinated children.

The Path Forward: Optimizing Varicella Immunity Assessment

While the VaccZyme™ VZV gpEIA kit shows promise as a reliable tool for measuring varicella antibody titers, the study highlights the need to re-evaluate current cutoff values to better align with the immune responses of vaccinated children. Optimizing these guidelines could improve the accuracy of immunity assessments, leading to more effective vaccination strategies and better protection against varicella. The information in this article provides important information on the accuracy of current testing methods for varicella immunity.

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This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3349/ymj.2014.55.2.459, Alternate LINK

Title: Evaluation Of A Commercial Glycoprotein Enzyme-Linked Immunosorbent Assay For Measuring Vaccine Immunity To Varicella

Subject: General Medicine

Journal: Yonsei Medical Journal

Publisher: Yonsei University College of Medicine

Authors: Yun Hwa Kim, Ji Young Hwang, Hye Min Shim, Eunsil Lee, Songyong Park, Hosun Park

Published: 2014-01-01

Everything You Need To Know

What is varicella and why is it important to understand it?

Varicella is a highly contagious disease caused by the varicella-zoster virus (VZV), commonly known as chickenpox. It has been significantly reduced due to the widespread use of the varicella vaccine. The significance of understanding varicella stems from the need to ensure that vaccination programs are effective and that individuals are adequately protected against the virus. Accurate measurement of immunity is important because breakthrough infections can still occur, meaning that even vaccinated individuals can contract the disease, which necessitates continuous evaluation and optimization of vaccination strategies.

What is the FAMA test and why is it considered the gold standard?

The fluorescent antibody to membrane antigen (FAMA) test is traditionally considered the 'gold standard' for detecting varicella antibodies. While highly accurate, the FAMA test is labor-intensive and not easily automated, making it less practical for large-scale testing. The importance of the FAMA test lies in its established reliability in detecting varicella antibodies. However, the limitations of the FAMA test led to the development and evaluation of alternative methods, such as the VaccZyme™ VZV gpEIA kit, to provide a more practical and standardized approach to assessing varicella immunity.

What is the VaccZyme™ VZV gpEIA kit and why is it important?

The VaccZyme™ VZV gpEIA kit is a serological assay designed to detect and quantify antibodies against VZV in the body. It measures IgG antibodies specific to VZV glycoproteins, using the WHO international standard as a calibrator, offering a potentially more convenient and standardized method for assessing varicella immunity. The importance of the VaccZyme™ VZV gpEIA kit lies in its potential to offer a more efficient and standardized method for assessing immunity compared to the FAMA test. The kit's accuracy is crucial for helping to determine whether current cutoff values for immunity are appropriate, especially in vaccinated children, which could lead to improved vaccine strategies.

What are cutoff values, and why are they important?

Cutoff values are the thresholds used to define immunity to varicella. These values are used to determine whether a person is considered immune or not based on the antibody levels detected by the tests. The importance of cutoff values is to guide the assessment of protection in vaccinated children. If the cutoff values are not optimal, it could lead to inaccurate assessments of immunity, which may affect the effectiveness of vaccination strategies. Current studies are evaluating whether these cutoff values need to be adjusted to better reflect the immune responses of vaccinated individuals.

What do sensitivity and specificity mean in the context of varicella immunity, and why are they important?

Sensitivity in the context of varicella immunity assessment refers to the ability of a test to correctly identify individuals who have antibodies against VZV and are thus considered immune. Specificity, on the other hand, refers to the test's ability to correctly identify individuals who do not have antibodies and are not immune. The significance of sensitivity and specificity lies in their impact on the accuracy of immunity assessments. Low sensitivity in the VaccZyme™ VZV gpEIA kit indicates that the kit might not correctly identify all vaccinated children who are protected against varicella. Optimizing these values can lead to more effective vaccination strategies and better protection against varicella.